We propose a simple adiabatic quantum spin pump to generate pure spin current. The spin pump is driven by an ac gate voltage and a time-dependent magnetic impurity potential. It is found that the total pumped spin per...We propose a simple adiabatic quantum spin pump to generate pure spin current. The spin pump is driven by an ac gate voltage and a time-dependent magnetic impurity potential. It is found that the total pumped spin per cycle exhibits oscillations, whose magnitude decays exponentially with changing strength of the impurity potential. The proposed method may be useful for spintronic applications.展开更多
We study the thermoelectric effect in a small quantum dot with a magnetic impurity in the Coulomb blockade regime. The electrical conductance, thermal conductance, thermopower, and the thermoelectrical figure of merit...We study the thermoelectric effect in a small quantum dot with a magnetic impurity in the Coulomb blockade regime. The electrical conductance, thermal conductance, thermopower, and the thermoelectrical figure of merit (FOM) are calcu- lated by using Green's function method. It is found that the peaks in the electrical conductance are split by the exchange coupling between the electron entering into the dot and the magnetic impurity inside the dot, accompanied by the decrease in the height of peaks. As a result, the resonances in the thermoelectric quantities, such as the thermal conductance, ther- mopower, and the FOM, are all split, opening some effective new working regions. Despite of the significant reduction in the height of the electrical conductance peaks induced by the exchange coupling, the values of the FOM and the ther-mopower can be as large as those in the case of zero exchange coupling. We also find that the thermoelectric efficiency, characterized by the magnitude of the FOM, can be enhanced by adjusting the left-right asymmetry of the electrode-dot coupling or by optimizing the system's temperature.展开更多
Aharonov-Casher oscillasions of transmission through a mesoscopic ring with a magnetic impurity is investigated. Both spin-dependent transmission and reflection coefficients of spin-state electrons at zero-temperature...Aharonov-Casher oscillasions of transmission through a mesoscopic ring with a magnetic impurity is investigated. Both spin-dependent transmission and reflection coefficients of spin-state electrons at zero-temperature are calculated as a function of the textured electric fields and its title angle in the present of spin-flipper scattering. It is found that the spin-exchange interaction can destroy intermittently periodic oscillations of spin-up transmission and reflection coefficients within some small ranges in the adiabatic region of quantum phase. However spin-down transmission and reflection coefficients appear periodic AC oscillations. The calculated results manifest that spindown transmission and reflection coefficients have the same perfect oscillation patterns. In the nonadiabatic region, the behavior of the anomalous AC oscillations are depedent on the difference between the tilt angle of spin and that of texture electric field.展开更多
The magnetic impurity scattering plays an important role in the phase coherence behavior of thin films.By using the thickness and disorder dependences of the low temperature logarithmic anomaly in resistivity we are a...The magnetic impurity scattering plays an important role in the phase coherence behavior of thin films.By using the thickness and disorder dependences of the low temperature logarithmic anomaly in resistivity we are able to determine the concentration of magnetic impurities in Au films and demonstrate that the low temperature saturation or plateau in phase decoherence time is closely related with the Kondo effect.展开更多
We theoretically investigate the Ruderman–Kittel–Kasuya–Yosida(RKKY) interaction in helical higher-order topological insulators(HOTIs), revealing distinct behaviors mediated by hinge and Dirac-type bulk carriers. O...We theoretically investigate the Ruderman–Kittel–Kasuya–Yosida(RKKY) interaction in helical higher-order topological insulators(HOTIs), revealing distinct behaviors mediated by hinge and Dirac-type bulk carriers. Our findings show that hinge-mediated interactions consist of Heisenberg, Ising, and Dzyaloshinskii–Moriya(DM) terms, exhibiting a decay with impurity spacing z and oscillations with Fermi energy εF. These interactions demonstrate ferromagnetic behaviors for the Heisenberg and Ising terms and alternating behavior for the DM term. In contrast, bulk-mediated interactions include Heisenberg, twisted Ising, and DM terms, with a conventional cubic oscillating decay. This study highlights the nuanced interplay between hinge and bulk RKKY interactions in HOTIs, offering insights into designs of next-generation quantum devices based on HOTIs.展开更多
One-dimensional(1D)topological insulators are superior for low-dissipation applications owing to the 1D character of surface states where scatterings other than prohibited backscattering are further restricted.Among t...One-dimensional(1D)topological insulators are superior for low-dissipation applications owing to the 1D character of surface states where scatterings other than prohibited backscattering are further restricted.Among the proposed candidates for 1D topological materials,TaNiTe_(5)has attracted intensive attention for its quasi-one-dimensional(quasi-1D)crystalline structure.In this study,we identify the chain-like construction and anisotropic electronic states on TaNiTe_5 surface with scanning tunneling microscopy.The electron scatterings are largely suppressed even with chromium impurities deposited on the surface and magnetic field applied normal to the surface,which endows TaNiTe_5 great potential for low-dissipation spintronic applications.展开更多
The impurities of exchange couplings, external magnetic fields and Dzyaloshinskii-Moriya (DM) interaction considered as Gaussian distribution, and the entanglement in one-dimensional random XY spin systems is invest...The impurities of exchange couplings, external magnetic fields and Dzyaloshinskii-Moriya (DM) interaction considered as Gaussian distribution, and the entanglement in one-dimensional random XY spin systems is investigated by the method of solving the different spin-spin correlation functions and the average magnetization per spin. The entanglement dynamics at central locations of ferromagnetic and antiferromagnetic chains have been studied by varying the three impurities and the strength of DM interaction. (i) For the ferromagnetic spin chain, the weak DM interaction can improve the amount of entanglement to a large value, and the impurities have the opposite effect on the entanglement below and above critical DM interaction. (ii) For the antiferromagnetic spin chain, DM interaction can enhance the entanglement to a steady value. Our results imply that DM interaction strength, the impurity and exchange couplings (or magnetic field) play competing roles in enhancing quantum entanglement.展开更多
Both impurity- and magnetic-field-induced quasiparticle states in chiral p-wave superconductors are investigated theoretically by solving the Bogoliubov-de Gennes equations self-consistently. At the strong scattering ...Both impurity- and magnetic-field-induced quasiparticle states in chiral p-wave superconductors are investigated theoretically by solving the Bogoliubov-de Gennes equations self-consistently. At the strong scattering limit, we find that a universal state bound to the impurity can be induced for both a single nonmagnetic impurity and a single magnetic impurity. Furthermore, we find that different chiral order parameters and the corresponding supercurrents have uniform distributions around linear impurities. Calculations of the local density of states in the presence of an external magnetic field show that the intensity peak of the zero-energy Majorana mode in the vortex core can be enhanced dramatically by tuning the strength of the external magnetic field or pairing interaction.展开更多
1.IntroductionSince the Nd-Fe-B magnets appearedin 1983,researchers,producers and users ofthe permanent magnetic materials have paidgreat attention to them.Because the mag-nets have low Curie temperature Tc andbad the...1.IntroductionSince the Nd-Fe-B magnets appearedin 1983,researchers,producers and users ofthe permanent magnetic materials have paidgreat attention to them.Because the mag-nets have low Curie temperature Tc andbad thermal stability as well as easeoxidation,their applications are limited insome fields.The researchers are greatly in-terested in increase energy product展开更多
In order to study the basic superconductivity properties of R2Pt3Ge5, we synthesized the single crystalline samples by the Pt–Ge self-flux method. R2Pt3Ge5(R = La, Ce) were also grown for a systematic study. Zero-r...In order to study the basic superconductivity properties of R2Pt3Ge5, we synthesized the single crystalline samples by the Pt–Ge self-flux method. R2Pt3Ge5(R = La, Ce) were also grown for a systematic study. Zero-resistivity was observed in both the La-and Pr-based samples below the reported superconducting transition temperatures. However, magnetic susceptibility measurements showed low superconductivity volume fractions in both La2Pt3Ge5 and R2Pt3Ge5(less than2%). Ce2Pt3Ge5 did not show any signature of superconductivity. From the specific heat measurements, we did not observe a superconducting transition peak in R2Pt3Ge5, suggesting that it is not a bulk superconductor. The magnetic susceptibility and heat capacity measurements revealed two antiferromagnetic(AFM) orders in R2Pt3Ge5 at T(N1)= 4.2 K and T(N2)= 3.5K, as well as a single AFM transition at TN= 3.8 K in Ce2Pt3Ge5.展开更多
Non-Hermitian systems have been discussed mostly in the context of open systems and nonequilibrium.Recent experimental progress is much from optical,cold-atomic,and classical platforms due to the vast tunability and c...Non-Hermitian systems have been discussed mostly in the context of open systems and nonequilibrium.Recent experimental progress is much from optical,cold-atomic,and classical platforms due to the vast tunability and clear identification of observables.However,their counterpart in solid-state electronic systems in equilibrium remains unmasked although highly desired,where a variety of materials are available,calculations are solidly founded,and accurate spectroscopic techniques can be applied.We demonstrate that,in the surface state of a topological insulator with spin-dependent relaxation due to magnetic impurities,highly nontrivial topological soliton spin textures appear in momentum space.Such spin-channel phenomena are delicately related to the type of non-Hermiticity and correctly reveal the most robust non-Hermitian features detectable spectroscopically.Moreover,the distinct topological soliton objects can be deformed to each other,mediated by topological transitions driven by tuning across a critical direction of doped magnetism.These results not only open a solid-state avenue to exotic spin patterns via spin-and angle-resolved photoemission spectroscopy,but also inspire non-Hermitian dissipation engineering of spins in solids.展开更多
基金supported by the State Key Program for Basic Research of China(Grant Nos.2015CB921202,2014CB921103,2011CB922103,and 2010CB923400)the National Natural Science Foundation of China(Grant Nos.11225420,11174125,and 91021003)the Priority Academic Program Development of Higher Education Institutions of Jiangsu Province,China
文摘We propose a simple adiabatic quantum spin pump to generate pure spin current. The spin pump is driven by an ac gate voltage and a time-dependent magnetic impurity potential. It is found that the total pumped spin per cycle exhibits oscillations, whose magnitude decays exponentially with changing strength of the impurity potential. The proposed method may be useful for spintronic applications.
基金Project supported by the National Natural Science Foundation of China(Grant No.61274101)the SKLSM(Grant No.CHJG200901)
文摘We study the thermoelectric effect in a small quantum dot with a magnetic impurity in the Coulomb blockade regime. The electrical conductance, thermal conductance, thermopower, and the thermoelectrical figure of merit (FOM) are calcu- lated by using Green's function method. It is found that the peaks in the electrical conductance are split by the exchange coupling between the electron entering into the dot and the magnetic impurity inside the dot, accompanied by the decrease in the height of peaks. As a result, the resonances in the thermoelectric quantities, such as the thermal conductance, ther- mopower, and the FOM, are all split, opening some effective new working regions. Despite of the significant reduction in the height of the electrical conductance peaks induced by the exchange coupling, the values of the FOM and the ther-mopower can be as large as those in the case of zero exchange coupling. We also find that the thermoelectric efficiency, characterized by the magnitude of the FOM, can be enhanced by adjusting the left-right asymmetry of the electrode-dot coupling or by optimizing the system's temperature.
文摘Aharonov-Casher oscillasions of transmission through a mesoscopic ring with a magnetic impurity is investigated. Both spin-dependent transmission and reflection coefficients of spin-state electrons at zero-temperature are calculated as a function of the textured electric fields and its title angle in the present of spin-flipper scattering. It is found that the spin-exchange interaction can destroy intermittently periodic oscillations of spin-up transmission and reflection coefficients within some small ranges in the adiabatic region of quantum phase. However spin-down transmission and reflection coefficients appear periodic AC oscillations. The calculated results manifest that spindown transmission and reflection coefficients have the same perfect oscillation patterns. In the nonadiabatic region, the behavior of the anomalous AC oscillations are depedent on the difference between the tilt angle of spin and that of texture electric field.
基金supported by the National Basic Research Program of China (Grant No. 2006CB91304)the Knowledge Innovation Project of Chinese Academy of Sciences
文摘The magnetic impurity scattering plays an important role in the phase coherence behavior of thin films.By using the thickness and disorder dependences of the low temperature logarithmic anomaly in resistivity we are able to determine the concentration of magnetic impurities in Au films and demonstrate that the low temperature saturation or plateau in phase decoherence time is closely related with the Kondo effect.
基金supported by the research foundation of Institute for Advanced Sciences of CQUPT(Grant No.E011A2022328)。
文摘We theoretically investigate the Ruderman–Kittel–Kasuya–Yosida(RKKY) interaction in helical higher-order topological insulators(HOTIs), revealing distinct behaviors mediated by hinge and Dirac-type bulk carriers. Our findings show that hinge-mediated interactions consist of Heisenberg, Ising, and Dzyaloshinskii–Moriya(DM) terms, exhibiting a decay with impurity spacing z and oscillations with Fermi energy εF. These interactions demonstrate ferromagnetic behaviors for the Heisenberg and Ising terms and alternating behavior for the DM term. In contrast, bulk-mediated interactions include Heisenberg, twisted Ising, and DM terms, with a conventional cubic oscillating decay. This study highlights the nuanced interplay between hinge and bulk RKKY interactions in HOTIs, offering insights into designs of next-generation quantum devices based on HOTIs.
基金the National Key R&D Program of China(Grant No.2017YFA0305400)the National Natural Science Foundation of China(Grant No.11227902)。
文摘One-dimensional(1D)topological insulators are superior for low-dissipation applications owing to the 1D character of surface states where scatterings other than prohibited backscattering are further restricted.Among the proposed candidates for 1D topological materials,TaNiTe_(5)has attracted intensive attention for its quasi-one-dimensional(quasi-1D)crystalline structure.In this study,we identify the chain-like construction and anisotropic electronic states on TaNiTe_5 surface with scanning tunneling microscopy.The electron scatterings are largely suppressed even with chromium impurities deposited on the surface and magnetic field applied normal to the surface,which endows TaNiTe_5 great potential for low-dissipation spintronic applications.
基金Supported by the Key Higher Education Programme of Hubei Province under Grant No Z20052201, the Natural Science Foundation of Hubei Province, China under Grant No 2006ABA055, and the Postgraduate Programme of Hubei Normal University under Grant No 2007D20.
文摘The impurities of exchange couplings, external magnetic fields and Dzyaloshinskii-Moriya (DM) interaction considered as Gaussian distribution, and the entanglement in one-dimensional random XY spin systems is investigated by the method of solving the different spin-spin correlation functions and the average magnetization per spin. The entanglement dynamics at central locations of ferromagnetic and antiferromagnetic chains have been studied by varying the three impurities and the strength of DM interaction. (i) For the ferromagnetic spin chain, the weak DM interaction can improve the amount of entanglement to a large value, and the impurities have the opposite effect on the entanglement below and above critical DM interaction. (ii) For the antiferromagnetic spin chain, DM interaction can enhance the entanglement to a steady value. Our results imply that DM interaction strength, the impurity and exchange couplings (or magnetic field) play competing roles in enhancing quantum entanglement.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant Nos. 11625416 and 11474064), the State Key Programs of China (Grant No. 2016YFA0300504), the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB04040300), and the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Grant No. 2016215).
文摘Both impurity- and magnetic-field-induced quasiparticle states in chiral p-wave superconductors are investigated theoretically by solving the Bogoliubov-de Gennes equations self-consistently. At the strong scattering limit, we find that a universal state bound to the impurity can be induced for both a single nonmagnetic impurity and a single magnetic impurity. Furthermore, we find that different chiral order parameters and the corresponding supercurrents have uniform distributions around linear impurities. Calculations of the local density of states in the presence of an external magnetic field show that the intensity peak of the zero-energy Majorana mode in the vortex core can be enhanced dramatically by tuning the strength of the external magnetic field or pairing interaction.
文摘1.IntroductionSince the Nd-Fe-B magnets appearedin 1983,researchers,producers and users ofthe permanent magnetic materials have paidgreat attention to them.Because the mag-nets have low Curie temperature Tc andbad thermal stability as well as easeoxidation,their applications are limited insome fields.The researchers are greatly in-terested in increase energy product
基金Project supported by the National Natural Science Foundation of China(Grant No.11204041)STCSM of China(Grant No.15XD1500200)
文摘In order to study the basic superconductivity properties of R2Pt3Ge5, we synthesized the single crystalline samples by the Pt–Ge self-flux method. R2Pt3Ge5(R = La, Ce) were also grown for a systematic study. Zero-resistivity was observed in both the La-and Pr-based samples below the reported superconducting transition temperatures. However, magnetic susceptibility measurements showed low superconductivity volume fractions in both La2Pt3Ge5 and R2Pt3Ge5(less than2%). Ce2Pt3Ge5 did not show any signature of superconductivity. From the specific heat measurements, we did not observe a superconducting transition peak in R2Pt3Ge5, suggesting that it is not a bulk superconductor. The magnetic susceptibility and heat capacity measurements revealed two antiferromagnetic(AFM) orders in R2Pt3Ge5 at T(N1)= 4.2 K and T(N2)= 3.5K, as well as a single AFM transition at TN= 3.8 K in Ce2Pt3Ge5.
基金supported by JSPS KAKENHI(18H03676)JST CREST(JPMJCR1874)supported by RIKEN Special Postdoctoral Researcher Program。
文摘Non-Hermitian systems have been discussed mostly in the context of open systems and nonequilibrium.Recent experimental progress is much from optical,cold-atomic,and classical platforms due to the vast tunability and clear identification of observables.However,their counterpart in solid-state electronic systems in equilibrium remains unmasked although highly desired,where a variety of materials are available,calculations are solidly founded,and accurate spectroscopic techniques can be applied.We demonstrate that,in the surface state of a topological insulator with spin-dependent relaxation due to magnetic impurities,highly nontrivial topological soliton spin textures appear in momentum space.Such spin-channel phenomena are delicately related to the type of non-Hermiticity and correctly reveal the most robust non-Hermitian features detectable spectroscopically.Moreover,the distinct topological soliton objects can be deformed to each other,mediated by topological transitions driven by tuning across a critical direction of doped magnetism.These results not only open a solid-state avenue to exotic spin patterns via spin-and angle-resolved photoemission spectroscopy,but also inspire non-Hermitian dissipation engineering of spins in solids.